Typically, a manual bypass tray is attached to one side of an image forming apparatus, such as a copier, printer, facsimile or multifunctional peripheral combining the above functions. On the manual bypass tray, the following are arranged: a flapper that can swing in a vertical direction, a spring that continually urges the flapper upward with an elastic force and consequently allows the flapper to come into contact with a paper feed roller which is provided on a main unit end side of the flapper, a lever used to push the flapper downward and to release the pushed-down condition, and a separation pad made of an elastic member such as rubber that is elastically contacted with the paper feed roller.
The above paper feeder is configured so that when the paper feed roller is rotated while the sheets of paper loaded on the flapper are pressed against thereon, the sheets of paper can be fed to a paper conveying mechanism in response to rotation of the paper feed roller.
Some models of image forming apparatus require a user to push the flapper downward when the user loads sheets of paper on a manual bypass tray. In particular, some of low grade models manufactured at a low cost require the above operation. Once a user pushes the flapper downward, a vertical clearance is formed between a case of an apparatus and the flapper. Thus, when a user loads sheets of paper on the flapper under this circumstance, the user can put the edge of the sheets of paper to the depth of the flapper in a paper feeding direction. Then, when the pushed-down condition is released so as to push the flapper upward with an urging force of the spring, the sheets of paper can be properly positioned at a position where the sheets of paper are nipped between the paper feed roller and the separation pad. The sheets of paper properly nipped between the paper feed roller and the separation pad are fed to a paper conveying mechanism one by one in response to the rotation of the paper feed roller.
Generally, with the above described low grade models, while the manual bypass tray is opened, a vertical narrow clearance is already formed between the case and the flapper even before the flapper is pushed downward. Therefore, some users sometimes load sheets of paper on the flapper without pushing it downward and try to put (insert) the sheets of paper forcibly into the clearance formed above the flapper in an improper way.
While the flapper is not pushed downward, the vertical clearance between the flapper and the case is not wide enough. Therefore, when the sheets of paper are loaded on the flapper before the flapper is pushed downward, insertion of the sheets of paper into the clearance stops before the edge of the sheets of paper reaches the nipping position, that is, the insertion stops at an upstream side in the paper feeding direction and consequently the sheets of paper are not positioned at a proper position where the sheets of paper are nipped between the paper feed roller and the separation pad.
Most models of the image forming apparatus includes a sensor at this side of the paper feed roller (on an upstream side in the paper feeding direction) to sense whether a sheet (s) of paper is (are) loaded or not. When a command for printing operation is given after the sensor senses that the sheet(s) of paper is (are) loaded, a control unit provided in the image forming apparatus allows the paper feed roller to start rotating.
Even if sheets of paper are loaded on the flapper before the flapper is pushed downward, as the sheets of paper have reached a position close to a paper feed roller, some sensors might sense a presence of the sheets of paper loaded. Therefore, once a command for printing operation is given, the paper feed roller starts rotating. However, as the sheets of paper is not nipped properly between the paper feed roller and the separation pad, the paper feed roller cannot hold the sheets of paper properly and consequently cannot feed the sheets of paper to the paper conveying mechanism. Accordingly, the control unit recognizes that an error in paper setting has occurred and has a control panel indicate a notification on the loading error.
In this case, a user is at a loss as to why the error notification on paper setting is displayed although the sheets of paper has been loaded, and accordingly the user may spend a lot of time to identify the cause for the error. Further, in a case where a plurality of users share the same image forming apparatus in an office and the like, a similar error notification might be frequently displayed.
Some relatively expensive models of the image forming apparatus are configured so that the flapper is automatically pushed downward in accordance with opening of a manual bypass tray. In such a configuration, the above problem is unlikely to occur. However, in order to add such a function, a lot of components or controlling mechanisms need to be installed to such a lower grade model. Therefore, it will be difficult to provide the model with the function at a similar price range with the low grade model. Furthermore, for users who have already purchased such a low grade model, it is not easy to newly replace the image forming apparatus in order only to decrease the frequency of the occurrence of the above described error.
There is a need in the art for a paper feeder for an image forming apparatus in which a function to prevent errors in paper loading (errors in printing operation) has been included by adding a simple structure.